1. Field of the Invention
This invention relates to a metal seal, especially, a metal seal disposed between a pair of flat faces as to perform sealing function with torsional deformation.
2. Description of the Related Art
Conventionally, metal seals are often used under harsh conditions such as high vacuum and high pressure (outer and inner pressure), high temperature and low temperature, or sealing corrosive fluid, etc.
So the inventors of the present invention had proposed a metal seal having a configuration (construction) shown in FIG. 6 and FIG. 7, which is disposed between a pair of flat faces to perform sealing function with torsional deformation as described above with small fastening force and high recovering force (refer to Japanese patent No. 4091373, for example).
A conventional metal seal 30 shown in FIG. 6 and FIG. 7, in which torsional elastic deformation is generated, is disposed between a pair of mutually parallel flat faces 31 and 32, and of which cross-sectional configuration is a block type having a rectangular middle base portion 33 and half-circular contact convex portions 34 and 35. The material is metal such as SUS, and the metal seal is constructed as that the half-circular contact convex portions 34 and 35 are pressed to the pair of flat faces 31 and 32 with a predetermined pressure distribution 36 to perform fluid sealing function in a final approaching state (final assembly state) with torsional elastic deformation shown in FIG. 7 in which the flat faces 31 and 32 in a free state (unattached state) shown in FIG. 6 are made mutually come close as shown in FIG. 7.
As clearly shown in FIG. 7, the half-circular contact convex portions 34 and 35 have maximum pressure P0 in contact with the flat faces 31 and 32, rather large contact arc length C0, and the pressure distribution 36 of relatively gentle hill shape.
The conventional metal seal 30 as described above, although having an advantage that the flat faces 31 and 32 as corresponding faces are not damaged, leaves following problems. That is to say, (i) the flat faces 31 and 32 are necessary to be mirror-finished, (ii) the contact convex portions 34 and 35 of the metal seal 30 are necessary to be finished with super polishing, and (iii) sealability is rather insufficient for sealing gas, can be pointed out.
It is therefore an object of the present invention to provide a metal seal with which the above mentioned problems (i) (ii) (iii) are resolved with a simple configuration, and strict quality control of sealing face portions such as the mirror finish and the super polishing finish on the corresponding faces (flat faces) and the metal seal itself can be omitted to facilitate the production and lower the cost. And, it is another object to improve the sealability further.